Hi Zhoujian,
2017-05-17 10:20 GMT+08:00 Zhoujian (jay) <jianjay.z...@huawei.com>:
> Hi Wanpeng,
>
>> > On 11/05/2017 14:07, Zhoujian (jay) wrote:
>> >> - * Scan sptes if dirty logging has been stopped, dropping those
>> >> - * which can be collapsed into a single large-page spte. Later
>> >> - * page faults will create the large-page sptes.
>> >> + * Reset each vcpu's mmu, then page faults will create the
>> large-page
>> >> + * sptes later.
>> >> */
>> >> if ((change != KVM_MR_DELETE) &&
>> >> (old->flags & KVM_MEM_LOG_DIRTY_PAGES) &&
>> >> - !(new->flags & KVM_MEM_LOG_DIRTY_PAGES))
>> >> - kvm_mmu_zap_collapsible_sptes(kvm, new);
>>
>> This is an unlikely branch(unless guest live migration fails and continue
>> to run on the source machine) instead of hot path, do you have any
>> performance number for your real workloads?
>>
>
> Sorry to bother you again.
>
> Recently, I have tested the performance before migration and after migration
> failure
> using spec cpu2006 https://www.spec.org/cpu2006/, which is a standard
> performance
> evaluation tool.
>
> These are the results:
> ******
> Before migration the score is 153, and the TLB miss statistics of the
> qemu process is:
> linux-sjrfac:/mnt/zhoujian # perf stat -e
> dTLB-load-misses,dTLB-loads,dTLB-store-misses, \
> dTLB-stores,iTLB-load-misses,iTLB-loads -p 26463 sleep 10
>
> Performance counter stats for process id '26463':
>
> 698,938 dTLB-load-misses # 0.13% of all dTLB
> cache hits (50.46%)
> 543,303,875 dTLB-loads
> (50.43%)
> 199,597 dTLB-store-misses
> (16.51%)
> 60,128,561 dTLB-stores
> (16.67%)
> 69,986 iTLB-load-misses # 6.17% of all iTLB
> cache hits (16.67%)
> 1,134,097 iTLB-loads
> (33.33%)
>
> 10.000684064 seconds time elapsed
>
> After migration failure the score is 149, and the TLB miss statistics of
> the qemu process is:
> linux-sjrfac:/mnt/zhoujian # perf stat -e
> dTLB-load-misses,dTLB-loads,dTLB-store-misses, \
> dTLB-stores,iTLB-load-misses,iTLB-loads -p 26463 sleep 10
>
> Performance counter stats for process id '26463':
>
> 765,400 dTLB-load-misses # 0.14% of all dTLB
> cache hits (50.50%)
> 540,972,144 dTLB-loads
> (50.47%)
> 207,670 dTLB-store-misses
> (16.50%)
> 58,363,787 dTLB-stores
> (16.67%)
> 109,772 iTLB-load-misses # 9.52% of all iTLB
> cache hits (16.67%)
> 1,152,784 iTLB-loads
> (33.32%)
>
> 10.000703078 seconds time elapsed
> ******
Could you comment out the original "lazy collapse small sptes into
large sptes" codes in the function kvm_arch_commit_memory_region() and
post the results here?
Regards,
Wanpeng Li
>
> These are the steps:
> ======
> (1) the version of kmod is 4.4.11(with slightly modified) and the version of
> qemu is 2.6.0
> (with slightly modified), the kmod is applied with the following patch
> according to
> Paolo's advice:
>
> diff --git a/source/x86/x86.c b/source/x86/x86.c
> index 054a7d3..75a4bb3 100644
> --- a/source/x86/x86.c
> +++ b/source/x86/x86.c
> @@ -8550,8 +8550,10 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
> */
> if ((change != KVM_MR_DELETE) &&
> (old->flags & KVM_MEM_LOG_DIRTY_PAGES) &&
> - !(new->flags & KVM_MEM_LOG_DIRTY_PAGES))
> - kvm_mmu_zap_collapsible_sptes(kvm, new);
> + !(new->flags & KVM_MEM_LOG_DIRTY_PAGES)) {
> + printk(KERN_ERR "zj make KVM_REQ_MMU_RELOAD request\n");
> + kvm_make_all_cpus_request(kvm, KVM_REQ_MMU_RELOAD);
> + }
>
> /*
> * Set up write protection and/or dirty logging for the new slot.
>
> (2) I started up a memory preoccupied 10G VM(suse11sp3), which means its "RES
> column" in top is 10G,
> in order to set up the EPT table in advance.
> (3) And then, I run the test case 429.mcf of spec cpu2006 before migration
> and after migration failure.
> The 429.mcf is a memory intensive workload, and the migration failure is
> constructed deliberately
> with the following patch of qemu:
>
> diff --git a/migration/migration.c b/migration/migration.c
> index 5d725d0..88dfc59 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -625,6 +625,9 @@ static void process_incoming_migration_co(void *opaque)
> MIGRATION_STATUS_ACTIVE);
> ret = qemu_loadvm_state(f);
>
> + // deliberately construct the migration failure
> + exit(EXIT_FAILURE);
> +
> ps = postcopy_state_get();
> trace_process_incoming_migration_co_end(ret, ps);
> if (ps != POSTCOPY_INCOMING_NONE) {
> ======
>
>
> Results of the score and TLB miss rate are almost the same, and I am confused.
> May I ask which tool do you use to evaluate the performance?
> And if my test steps are wrong, please let me know, thank you.
>
> Regards,
> Jay Zhou
>
>
>
>
>
